1 /*
2  * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
3  * Copyright (C) 2003 Daniel M. Eischen <deischen@freebsd.org>
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice unmodified, this list of conditions, and the following
11  *    disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26  *
27  * $DragonFly: src/lib/libthread_xu/thread/thr_list.c,v 1.5 2006/03/12 12:25:57 davidxu Exp $
28  */
29 
30 #include <sys/cdefs.h>
31 #include <sys/types.h>
32 #include <sys/queue.h>
33 
34 #include <stdlib.h>
35 #include <string.h>
36 #include <pthread.h>
37 
38 #include "thr_private.h"
39 #include "libc_private.h"
40 
41 /* #define DEBUG_THREAD_LIST */
42 #ifdef DEBUG_THREAD_LIST
43 #define DBG_MSG		stdout_debug
44 #else
45 #define DBG_MSG(x...)
46 #endif
47 
48 /*
49  * Define a high water mark for the maximum number of threads that
50  * will be cached.  Once this level is reached, any extra threads
51  * will be free()'d.
52  */
53 #define	MAX_CACHED_THREADS	100
54 
55 /*
56  * We've got to keep track of everything that is allocated, not only
57  * to have a speedy free list, but also so they can be deallocated
58  * after a fork().
59  */
60 static TAILQ_HEAD(, pthread)	free_threadq;
61 static umtx_t			free_thread_lock;
62 static umtx_t			tcb_lock;
63 static int			free_thread_count = 0;
64 static int			inited = 0;
65 static u_int64_t		next_uniqueid = 1;
66 
67 LIST_HEAD(thread_hash_head, pthread);
68 #define HASH_QUEUES	128
69 static struct thread_hash_head	thr_hashtable[HASH_QUEUES];
70 #define	THREAD_HASH(thrd)	(((unsigned long)thrd >> 12) % HASH_QUEUES)
71 
72 static void thr_destroy(struct pthread *curthread, struct pthread *thread);
73 
74 void
75 _thr_list_init(void)
76 {
77 	int i;
78 
79 	_gc_count = 0;
80 	_thr_umtx_init(&_thr_list_lock);
81 	TAILQ_INIT(&_thread_list);
82 	TAILQ_INIT(&free_threadq);
83 	_thr_umtx_init(&free_thread_lock);
84 	_thr_umtx_init(&tcb_lock);
85 	if (inited) {
86 		for (i = 0; i < HASH_QUEUES; ++i)
87 			LIST_INIT(&thr_hashtable[i]);
88 	}
89 	inited = 1;
90 }
91 
92 void
93 _thr_gc(struct pthread *curthread)
94 {
95 	struct pthread *td, *td_next;
96 	TAILQ_HEAD(, pthread) worklist;
97 
98 	TAILQ_INIT(&worklist);
99 	THREAD_LIST_LOCK(curthread);
100 
101 	/* Check the threads waiting for GC. */
102 	for (td = TAILQ_FIRST(&_thread_gc_list); td != NULL; td = td_next) {
103 		td_next = TAILQ_NEXT(td, gcle);
104 		if (td->terminated == 0) {
105 			/* make sure we are not still in userland */
106 			continue;
107 		}
108 		_thr_stack_free(&td->attr);
109 		if (((td->tlflags & TLFLAGS_DETACHED) != 0) &&
110 		    (td->refcount == 0)) {
111 			THR_GCLIST_REMOVE(td);
112 			/*
113 			 * The thread has detached and is no longer
114 			 * referenced.  It is safe to remove all
115 			 * remnants of the thread.
116 			 */
117 			THR_LIST_REMOVE(td);
118 			TAILQ_INSERT_HEAD(&worklist, td, gcle);
119 		}
120 	}
121 	THREAD_LIST_UNLOCK(curthread);
122 
123 	while ((td = TAILQ_FIRST(&worklist)) != NULL) {
124 		TAILQ_REMOVE(&worklist, td, gcle);
125 		/*
126 		 * XXX we don't free initial thread, because there might
127 		 * have some code referencing initial thread.
128 		 */
129 		if (td == _thr_initial) {
130 			DBG_MSG("Initial thread won't be freed\n");
131 			continue;
132 		}
133 
134 		_thr_free(curthread, td);
135 	}
136 }
137 
138 struct pthread *
139 _thr_alloc(struct pthread *curthread)
140 {
141 	struct pthread	*thread = NULL;
142 	struct tls_tcb	*tcb;
143 
144 	if (curthread != NULL) {
145 		if (GC_NEEDED())
146 			_thr_gc(curthread);
147 		if (free_thread_count > 0) {
148 			THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
149 			if ((thread = TAILQ_FIRST(&free_threadq)) != NULL) {
150 				TAILQ_REMOVE(&free_threadq, thread, tle);
151 				free_thread_count--;
152 			}
153 			THR_LOCK_RELEASE(curthread, &free_thread_lock);
154 		}
155 	}
156 	if (thread == NULL) {
157 		thread = malloc(sizeof(struct pthread));
158 		if (thread == NULL)
159 			return (NULL);
160 	}
161 	if (curthread != NULL) {
162 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
163 		tcb = _tcb_ctor(thread, 0 /* not initial tls */);
164 		THR_LOCK_RELEASE(curthread, &tcb_lock);
165 	} else {
166 		tcb = _tcb_ctor(thread, 1 /* initial tls */);
167 	}
168 	if (tcb != NULL) {
169 		memset(thread, 0, sizeof(*thread));
170 		thread->tcb = tcb;
171 	} else {
172 		thr_destroy(curthread, thread);
173 		thread = NULL;
174 	}
175 	return (thread);
176 }
177 
178 void
179 _thr_free(struct pthread *curthread, struct pthread *thread)
180 {
181 	DBG_MSG("Freeing thread %p\n", thread);
182 	if (thread->name) {
183 		free(thread->name);
184 		thread->name = NULL;
185 	}
186 	/*
187 	 * Always free tcb, as we only know it is part of RTLD TLS
188 	 * block, but don't know its detail and can not assume how
189 	 * it works, so better to avoid caching it here.
190 	 */
191 	if (curthread != NULL) {
192 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
193 		_tcb_dtor(thread->tcb);
194 		THR_LOCK_RELEASE(curthread, &tcb_lock);
195 	} else {
196 		_tcb_dtor(thread->tcb);
197 	}
198 	thread->tcb = NULL;
199 	if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
200 		thr_destroy(curthread, thread);
201 	} else {
202 		/*
203 		 * Add the thread to the free thread list, this also avoids
204 		 * pthread id is reused too quickly, may help some buggy apps.
205 		 */
206 		THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
207 		TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
208 		free_thread_count++;
209 		THR_LOCK_RELEASE(curthread, &free_thread_lock);
210 	}
211 }
212 
213 static void
214 thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
215 {
216 	free(thread);
217 }
218 
219 /*
220  * Add an active thread:
221  *
222  *   o Assign the thread a unique id (which GDB uses to track
223  *     threads.
224  *   o Add the thread to the list of all threads and increment
225  *     number of active threads.
226  */
227 void
228 _thr_link(struct pthread *curthread, struct pthread *thread)
229 {
230 	THREAD_LIST_LOCK(curthread);
231 	/*
232 	 * Initialize the unique id (which GDB uses to track
233 	 * threads), add the thread to the list of all threads,
234 	 * and
235 	 */
236 	thread->uniqueid = next_uniqueid++;
237 	THR_LIST_ADD(thread);
238 	_thread_active_threads++;
239 	THREAD_LIST_UNLOCK(curthread);
240 }
241 
242 /*
243  * Remove an active thread.
244  */
245 void
246 _thr_unlink(struct pthread *curthread, struct pthread *thread)
247 {
248 	THREAD_LIST_LOCK(curthread);
249 	THR_LIST_REMOVE(thread);
250 	_thread_active_threads--;
251 	THREAD_LIST_UNLOCK(curthread);
252 }
253 
254 void
255 _thr_hash_add(struct pthread *thread)
256 {
257 	struct thread_hash_head *head;
258 
259 	head = &thr_hashtable[THREAD_HASH(thread)];
260 	LIST_INSERT_HEAD(head, thread, hle);
261 }
262 
263 void
264 _thr_hash_remove(struct pthread *thread)
265 {
266 	LIST_REMOVE(thread, hle);
267 }
268 
269 struct pthread *
270 _thr_hash_find(struct pthread *thread)
271 {
272 	struct pthread *td;
273 	struct thread_hash_head *head;
274 
275 	head = &thr_hashtable[THREAD_HASH(thread)];
276 	LIST_FOREACH(td, head, hle) {
277 		if (td == thread)
278 			return (thread);
279 	}
280 	return (NULL);
281 }
282 
283 /*
284  * Find a thread in the linked list of active threads and add a reference
285  * to it.  Threads with positive reference counts will not be deallocated
286  * until all references are released.
287  */
288 int
289 _thr_ref_add(struct pthread *curthread, struct pthread *thread,
290     int include_dead)
291 {
292 	int ret;
293 
294 	if (thread == NULL)
295 		/* Invalid thread: */
296 		return (EINVAL);
297 
298 	THREAD_LIST_LOCK(curthread);
299 	if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
300 		thread->refcount++;
301 	}
302 	THREAD_LIST_UNLOCK(curthread);
303 
304 	/* Return zero if the thread exists: */
305 	return (ret);
306 }
307 
308 void
309 _thr_ref_delete(struct pthread *curthread, struct pthread *thread)
310 {
311 	THREAD_LIST_LOCK(curthread);
312 	_thr_ref_delete_unlocked(curthread, thread);
313 	THREAD_LIST_UNLOCK(curthread);
314 }
315 
316 void
317 _thr_ref_delete_unlocked(struct pthread *curthread, struct pthread *thread)
318 {
319 	if (thread != NULL) {
320 		thread->refcount--;
321 		if ((thread->refcount == 0) && thread->state == PS_DEAD &&
322 		    (thread->tlflags & TLFLAGS_DETACHED) != 0)
323 			THR_GCLIST_ADD(thread);
324 	}
325 }
326 
327 int
328 _thr_find_thread(struct pthread *curthread, struct pthread *thread,
329     int include_dead)
330 {
331 	struct pthread *pthread;
332 
333 	if (thread == NULL)
334 		/* Invalid thread: */
335 		return (EINVAL);
336 
337 	pthread = _thr_hash_find(thread);
338 	if (pthread) {
339 		if (include_dead == 0 && pthread->state == PS_DEAD) {
340 			pthread = NULL;
341 		}
342 	}
343 
344 	/* Return zero if the thread exists: */
345 	return ((pthread != NULL) ? 0 : ESRCH);
346 }
347